DNA Ancestry Tests
If race isn’t biological, how do DNA ancestry tests work?
DNA ancestry tests have been around for over a decade, and according to MIT Technology Review, over 26 million consumers have taken DNA ancestry tests through ancestry testing companies. Ancestry tests examine genetic patterns in a person’s DNA to find or verify ancestral origins, genetic relatives, or to estimate an individual’s ethnic makeup. Although these tests can give insights into a person’s family history, they cannot determine a person’s race. Let’s discuss how these test work and what they can really tell you about yourself.
To complete a DNA ancestry test, customers send a sample—normally their saliva—to a lab. At the lab, the DNA is extracted from the sample and sequenced. Sequencing helps determine which genetic variations a person has for a given trait or section of DNA. The DNA in that sample is then compared to a reference panel of DNA samples from people around the world. A reference panel is a selection of individuals that have genotypes that the testing company decides are the most typical or common among people in a specific group or region. Reference panels can be made from as few as 50 individuals to as many as 3000+. The individuals in a reference panel are selected because the company has determined that together they capture the best snapshot of the range of genetic variation in that group.
Testing companies try to estimate a person’s ethnic background by comparing sample DNA with the reference panel and finding out which groups have the most similar genotypes to the customer’s DNA sample. All human beings are 99.9% identical in their genetic makeup. DNA ancestry tests examine differences in the remaining 0.1% of genetic material that is not identical between all humans. However, human genetic diversity is not organized into neat groups like countries or continents. Results from DNA ancestry tests can only provide consumers with a set of probabilities of where you are most likely to have relatives living today, rather than accurate ethnic compositions.
Reference panels can be made from as few as 50 individuals to as many as 3000.
What are the limitations of DNA ancestry tests?
DNA ancestry tests are never 100% accurate. Different DNA ancestry testing companies use different reference populations, which can affect the results of these tests. Reference populations do not always show the full range of genetic diversity in a population, and companies do not always explain how their reference populations are created. While your DNA remains the same, testing with different companies can yield different results. Even identical twins taking the same DNA ancestry test can have varying results! In 2018, CBC News chronicled identical twins Charlsie and Carly Agro’s experience using five different DNA ancestry testing companies.
Source: CBC News
Identical twins have nearly identical DNA, yet the results of the Agro twins’ ancestry tests did not match across any of the five companies tested. When Geneticists from Yale University examined the Agro twins DNA and the results of these tests, they determined that the differences were likely due to the algorithms used by the testing companies, as well as the size and composition of reference populations. The Agro twins’ experience highlights the limitations of DNA ancestry testing companies.
DNA Ancestry Testing and Race
DNA ancestry tests can influence the relationship between race and self-identification. Misinterpreting the results of a DNA ancestry test can lead consumers to believe that the test can tell them what race they are, inadvertently reinforcing the idea that there are biological differences between races. DNA ancestry tests can also be used for spiteful intent, including to “prove” racial purity or superiority.
DNA ancestry tests can only determine genetic relationships between individuals. This bypasses the role of cultural and societal factors that help to shape a person’s identity. Although these tests can offer insights into genetic ancestry, they cannot capture the many factors that shape personal identity.
